Cardiac pacemakers which are implemented for the purpose of estimating a hematocrit value on the basis of a blood conductivity measurement or blood impedance measurement are known from the prior art, for example, from WO 2006/017446.
The device known from WO 2006/017446 uses the fact that the electrical conductivity of the blood is primarily a function of the particular hematocrit value.
The hematocrit value (HCT) refers to the volume proportion of cellular components and is a measure of the viscosity of the blood.
In addition, the hematocrit value is an important physiological variable whose observation permits conclusions about the pathophysiological state of a particular patient. In particular, changes of the particular hematocrit value are of interest here. The observation of the change of a particular hematocrit value may be used for the purpose of optimizing a particular medication treatment.
Typical methods known from the prior art for determining the hematocrit value are based on centrifuging, counting the erythrocytes, optical methods, or impedance measurement.
In addition, a particular known hematocrit value may be used as a correction value when determining the thorax impedance, as is known from US 2006/0041280.